perimenopause

physiology

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Last updated

July 17, 2026

Quick Summary

Perimenopause is the transitional period leading up to menopause, typically starting around age 40 and lasting for several years. During this time, a woman's ovaries begin to decline in function, leading to irregular menstrual cycles and fluctuating hormone levels, particularly estrogen.12

Key physiological changes include:
* Ovarian Function Decline: Follicles in the ovaries may fail to mature or release eggs, and estrogen levels decrease significantly in the final years of perimenopause.2
* Hormonal Shifts: This decrease in estrogen, along with changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH), can trigger various symptoms.2
* Menstrual Irregularity: Periods may become unpredictable, with missed cycles, shorter or longer intervals between periods, or changes in flow.2

While perimenopause can begin before menstruation ceases, symptoms like hot flashes are more likely to start after periods have ended.2

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menopause
Menopause and ovarian function
…a transitional phase known as perimenopause which can begin as early as 10 years before menopause, first some follicles and later all follicles fail to rupture and release their ova. In the last one or two years of perimenopause, estrogen levels decline quickly.
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…a transitional phase known as perimenopause which can begin as early as 10 years before menopause, first some follicles and later all follicles fail to rupture and release their ova. In the last one or two years of perimenopause, estrogen levels decline quickly.
Read More